When carrying out chemical or biochemical analyses, assays, syntheses or preparations, a large number of separate manipulations are performed on the material(s) or component(s) to be assayed, including measuring, aliquotting, transferring, diluting, mixing, separating, detecting, incubating, etc. Microfluidic technology miniaturizes these manipulations and integrates them so that they can be executed within one or a few microfluidic devices. For example, pioneering microfluidic methods of performing biological assays in microfluidic systems have been developed, such as those described by U.S. Pat. Nos. 5,942,443 and 6,235,471.
Of particular concern in numerous applications utilizing microfluidic devices is the dilution or mixing of, e.g., samples, reagents, analytes, etc. often within the small-scale microchannels comprising the device. Additionally, in many experimental/assay situations it is desirous to store biological or other molecules in storage solutions such as dimethyl sulfoxide (DMSO). However, because storage solutions, such as DMSO, can adversely affect certain types of assays, etc. and/or in order to present the molecule(s) in the storage solution (e.g., DMSO) in the correct concentration, such solution is typically diluted with other fluidic materials. Unfortunately, sudden diluting of some storage solutions (e.g., DMSO) can cause precipitates to come out of solution and possibly create a precipitate blockage of a microchannel or other microelement in the microfluidic device. Additionally, unwanted precipitate blockages can also arise through, e.g., precipitation of salts, proteins, etc. due to, e.g., changes in reaction conditions (such as temperature, concentration, pH, etc.) in the microfluidic elements. Because of the possibly extremely small scale diameters of the microfluidic elements in microfluidic devices, even small amounts of precipitate can achieve either total or partial blockage of microfluidic elements. Of course, such blockages can adversely impact flow through the microfluidic elements and thus adversely impact the assays, etc. being carried out in the microfluidic device. Furthermore, partial and/or complete blockages can, in some applications, adversely effect sample plug shape (e.g., width) etc. This is especially true in high throughput systems where even small interferences can severely decrease throughput efficiency.
A welcome addition to the art would be the ability to prevent or decrease the formation of blockages in microfluidic elements due to precipitation (especially due to that of DMSO). The current invention describes and provides these and other features by providing new methods, microchannels, and microfluidic devices that meet these and other goals.